The Internet is not powered by experiments on humans. Not even in the DARPA days.
No, websites do NOT experiment on users. Users may experiment on websites, if there's customization, but the rules for good design have not changed either in the past 30 years or the past 3,000. And, to judge from how humans organized carvings and paintings, not the past 30,000 either.
To say that websites experiment on people is tripe. Mouldy tripe. Websites may offer experimental views, surveys on what works, log analysis, etc, but these are statistical experiments on depersonalized aggregate data. Not people.
Experiments on people, especially without consent, is vulgar and wrong. It also doesn't help the website, because knowing what happens doesn't tell you why. Early experiments in AI are littered with extraordinarily bad results for this reason. Assuming you know why, assuming you can casually sketch in the cause merely by knowing one specific effect, is insanity.
Look, I will spell it out to these guys. Stop playing Sherlock Holmes, you only end up looking like Lestrade. Sir Conan Doyle's fictional hero used recursive subdivision, a technique Real Geeks use all the time for everything from decision trees to searching lists. Isolating single factors isn't subdivision because there isn't a single ordered space to subdivide. Scientists mask, yes, but only when dealing with single ordered spaces, and only AFTER producing a hypothesis. And if it involves research on humans, also after filling out a bloody great load of paperwork.
I flat-out refuse to use any website tainted with such puerile nonsense, insofar as I know it to have occurred. No matter how valuable that site may have been, it cannot remain valuable if it is driven by pseudoscience. There's also the matter of respect. If you don't respect me, why should I store any data with you? I can probably do better than most sites out there over a coffee break, so what's in it for me? What's so valuable that I should tolerate being second-class? It had better be damn good.
I'll take a temporary hit on what I can do, if it safeguards my absolute, unconditional control over my virtual persona. And temporary is all it would ever be. There's very little that's truly exclusive and even less that's exclusive and interesting.
The same is true of all users. We don't need any specific website, websites need us. We dictate our own limits, we dictate what safeguards are minimal, we dictate how far a site owner can go. Websites serve their users. They exist only to serve. And unlike with a certain elite class in the Dune series, that's actually true and enforceable.